The present invention relates to a process for manufacturing sealant coated articles. More particularly, the present invention relates to a process for manufacturing a heat recoverable polymeric article, a portion of which article possesses sealant properties.
Heat shrinkable tubing with a sealant coating on its interior surface has been used for many years in a variety of commercial applications. For example, sealant lined heat shrinkable tubing is used to insulate and seal electrical connections and to environmentally protect welded joints in pipe lines. Such sealant lined heat recoverable tubings are described in Wetmore, U.S. Pat. No. 3,297,819, the disclosure of which is incorporated by reference herein. Similarly, sealant coated, longitudinally heat shrinkable tape has been applied to metallic pipes, pipe joints and the like to provide corrosion protection.
Because of their relatively low viscosities and generally high tack, conventional sealant compositions do not readily lend themselves to processing in thermoplastic extrusion equipment. Heretofore, the best known process for manufacturing lengths of internally sealant coated heat shrinkable tubing entailed a costly separate coating step, which frequently had to be manually carried out on a discrete piece basis. In this prior art process, flexible, heat shrinkable tubing such as that described in Currie, U.S. Pat. No. 2,027,962 and in Cook et al., U.S. Pat. No. 3,086,242 is internally coated with a sealant applied with a brush or swab. Prior to application, the sealant composition is typically thinned with a solvent or heated to render it more fluid.
In contrast to the difficult problems encountered when coating a sealant material on the interior surface of a tubular article, a sealant layer can be applied to one surface of a longitudinally heat recoverable backing tape with relative ease. However, such a heat shrinkable tape fabrication process is not particularly efficient as it requires at least two relatively slow speed steps, one to produce the backing, and another separate step carried out subsequent to cross-linking the backing, to apply the coating thereto, again by swabbing or brushing.